Camilo José Vergara takes photographs of street art. A popular subject for the art he finds is Martin Luther King, Jr. who appears in murals in city after city. Smithsonian has a dozen of Vergara's pictures of these MLK installations, with some information about each one. The mural pictured here depicts the 1963 "I Have A Dream" speech, on a wall in Philadelphia. Link
Smithsonian also has the story behind the original photograph that became the iconic image of that speech. Link
(Image credit: Camilo José Vergara)